#include <stdio.h>
#include <string.h>
#include "db_packet.h"
#include "osint.h"

#ifndef TRUE
#define TRUE    1
#define FALSE   0
#endif

#define E
/* timeouts for waiting for ACK/NAK */
#define INITIAL_TIMEOUT     10000   // 10 seconds
#define PACKET_TIMEOUT      1000    // 1 second

/* packet format: SOH pkt# type length-lo length-hi hdrchk length*data crc1 crc2 */
#define HDR_SOH     0
#define HDR_PKTN    1
#define HDR_TYPE    2
#define HDR_LEN_HI  3
#define HDR_LEN_LO  4
#define HDR_CHK     5

/* packet header and crc lengths */
#define PKTHDRLEN   6
#define PKTCRCLEN   2

/* maximum length of a frame */
#define FRAMELEN    (PKTHDRLEN + PKTMAXLEN + PKTCRCLEN)

/* protocol characters */
#define SOH     0x01    /* start of a packet */
#define ACK     0x06    /* positive acknowledgement */
#define NAK     0x15    /* negative acknowledgement */
#define ESC     0x1b    /* escape from terminal mode */

#define updcrc(crc, ch) (crctab[((crc) >> 8) & 0xff] ^ ((crc) << 8) ^ (ch))

static const uint16_t crctab[256] = {
    0x0000,  0x1021,  0x2042,  0x3063,  0x4084,  0x50a5,  0x60c6,  0x70e7,
    0x8108,  0x9129,  0xa14a,  0xb16b,  0xc18c,  0xd1ad,  0xe1ce,  0xf1ef,
    0x1231,  0x0210,  0x3273,  0x2252,  0x52b5,  0x4294,  0x72f7,  0x62d6,
    0x9339,  0x8318,  0xb37b,  0xa35a,  0xd3bd,  0xc39c,  0xf3ff,  0xe3de,
    0x2462,  0x3443,  0x0420,  0x1401,  0x64e6,  0x74c7,  0x44a4,  0x5485,
    0xa56a,  0xb54b,  0x8528,  0x9509,  0xe5ee,  0xf5cf,  0xc5ac,  0xd58d,
    0x3653,  0x2672,  0x1611,  0x0630,  0x76d7,  0x66f6,  0x5695,  0x46b4,
    0xb75b,  0xa77a,  0x9719,  0x8738,  0xf7df,  0xe7fe,  0xd79d,  0xc7bc,
    0x48c4,  0x58e5,  0x6886,  0x78a7,  0x0840,  0x1861,  0x2802,  0x3823,
    0xc9cc,  0xd9ed,  0xe98e,  0xf9af,  0x8948,  0x9969,  0xa90a,  0xb92b,
    0x5af5,  0x4ad4,  0x7ab7,  0x6a96,  0x1a71,  0x0a50,  0x3a33,  0x2a12,
    0xdbfd,  0xcbdc,  0xfbbf,  0xeb9e,  0x9b79,  0x8b58,  0xbb3b,  0xab1a,
    0x6ca6,  0x7c87,  0x4ce4,  0x5cc5,  0x2c22,  0x3c03,  0x0c60,  0x1c41,
    0xedae,  0xfd8f,  0xcdec,  0xddcd,  0xad2a,  0xbd0b,  0x8d68,  0x9d49,
    0x7e97,  0x6eb6,  0x5ed5,  0x4ef4,  0x3e13,  0x2e32,  0x1e51,  0x0e70,
    0xff9f,  0xefbe,  0xdfdd,  0xcffc,  0xbf1b,  0xaf3a,  0x9f59,  0x8f78,
    0x9188,  0x81a9,  0xb1ca,  0xa1eb,  0xd10c,  0xc12d,  0xf14e,  0xe16f,
    0x1080,  0x00a1,  0x30c2,  0x20e3,  0x5004,  0x4025,  0x7046,  0x6067,
    0x83b9,  0x9398,  0xa3fb,  0xb3da,  0xc33d,  0xd31c,  0xe37f,  0xf35e,
    0x02b1,  0x1290,  0x22f3,  0x32d2,  0x4235,  0x5214,  0x6277,  0x7256,
    0xb5ea,  0xa5cb,  0x95a8,  0x8589,  0xf56e,  0xe54f,  0xd52c,  0xc50d,
    0x34e2,  0x24c3,  0x14a0,  0x0481,  0x7466,  0x6447,  0x5424,  0x4405,
    0xa7db,  0xb7fa,  0x8799,  0x97b8,  0xe75f,  0xf77e,  0xc71d,  0xd73c,
    0x26d3,  0x36f2,  0x0691,  0x16b0,  0x6657,  0x7676,  0x4615,  0x5634,
    0xd94c,  0xc96d,  0xf90e,  0xe92f,  0x99c8,  0x89e9,  0xb98a,  0xa9ab,
    0x5844,  0x4865,  0x7806,  0x6827,  0x18c0,  0x08e1,  0x3882,  0x28a3,
    0xcb7d,  0xdb5c,  0xeb3f,  0xfb1e,  0x8bf9,  0x9bd8,  0xabbb,  0xbb9a,
    0x4a75,  0x5a54,  0x6a37,  0x7a16,  0x0af1,  0x1ad0,  0x2ab3,  0x3a92,
    0xfd2e,  0xed0f,  0xdd6c,  0xcd4d,  0xbdaa,  0xad8b,  0x9de8,  0x8dc9,
    0x7c26,  0x6c07,  0x5c64,  0x4c45,  0x3ca2,  0x2c83,  0x1ce0,  0x0cc1,
    0xef1f,  0xff3e,  0xcf5d,  0xdf7c,  0xaf9b,  0xbfba,  0x8fd9,  0x9ff8,
    0x6e17,  0x7e36,  0x4e55,  0x5e74,  0x2e93,  0x3eb2,  0x0ed1,  0x1ef0
};

static uint8_t snd_pktn = 0;

static int WaitForAckNak(int timeout);

int WaitForInitialAck(void)
{
    return WaitForAckNak(INITIAL_TIMEOUT) == ACK;
}

int SendPacket(int type, uint8_t *buf, int len)
{
    uint8_t hdr[PKTHDRLEN], crc[PKTCRCLEN], *p;
    uint16_t crc16 = 0;
    int cnt, ch;

    /* setup the frame header */
    hdr[HDR_SOH] = SOH;                                 /* SOH */
    hdr[HDR_PKTN] = ++snd_pktn;                         /* packet# */
    hdr[HDR_TYPE] = type;                               /* type type */
    hdr[HDR_LEN_HI] = (uint8_t)(len >> 8);              /* data length - high byte */
    hdr[HDR_LEN_LO] = (uint8_t)len;                     /* data length - low byte */
    hdr[HDR_CHK] = hdr[1] + hdr[2] + hdr[3] + hdr[4];   /* header checksum */

    /* compute the crc */
    for (p = buf, cnt = len; --cnt >= 0; ++p)
        crc16 = updcrc(crc16, *p);
    crc16 = updcrc(crc16, '\0');
    crc16 = updcrc(crc16, '\0');

    /* add the crc to the frame */
    crc[0] = (uint8_t)(crc16 >> 8);
    crc[1] = (uint8_t)crc16;

    /* send the packet */
    tx(hdr, PKTHDRLEN);
    if (len > 0)
        tx(buf, len);
    tx(crc, PKTCRCLEN);

    /* wait for an ACK/NAK */
    if ((ch = WaitForAckNak(PACKET_TIMEOUT)) < 0) {
        printf("Timeout waiting for ACK/NAK\n");
        ch = NAK;
    }

    /* return status */
    return ch == ACK;
}

int ReceivePacket(int *pType, uint8_t *buf, int len)
{
    uint8_t hdr[PKTHDRLEN], crc[PKTCRCLEN];
    int actual_len, chk;
    uint16_t crc16 = 0;

    /* look for start of packet */
    do {
        rx(&hdr[HDR_SOH], 1);
    } while (hdr[HDR_SOH] != SOH);

    /* receive the rest of the header */
    rx(&hdr[HDR_PKTN], PKTHDRLEN - 1);

    /* check the header checksum */
    chk = (hdr[1] + hdr[2] + hdr[3] + hdr[4]) & 0xff;
    if (hdr[HDR_CHK] != chk)
        return -1;

    /* make sure the buffer is big enough for the payload */
    actual_len = hdr[HDR_LEN_HI] << 8 | hdr[HDR_LEN_LO];
    if (actual_len > len)
        return -1;
    
    /* receive the packet payload */
    rx(buf, actual_len);

    /* compute the crc */
    for (len = actual_len; --len >= 0; )
        crc16 = updcrc(crc16, *buf++);

    /* receive the crc */
    rx(crc, PKTCRCLEN);

    /* check the crc */
    crc16 = updcrc(crc16, crc[0]);
    crc16 = updcrc(crc16, crc[1]);
    if (crc16 != 0)
        return -1;

    /* return packet type and the length of the payload */
    *pType = hdr[HDR_TYPE];
    return actual_len;
}

static int WaitForAckNak(int timeout)
{
    uint8_t buf[1];
    return rx_timeout(buf, 1, timeout) == 1 ? buf[0] : -1;
}

void TerminalMode(void)
{
    printf("Entering terminal mode. Exit with ESC.\n");
    for (;;) {
        uint8_t buf[1];
        if (rx_timeout(buf, 1, 0) != SERIAL_TIMEOUT)
            console_putch(buf[0]);
        else if (console_kbhit()) {
            if ((buf[0] = console_getch()) == ESC)
                break;
            tx(buf, 1);
        }
    }
}
